[Intel-xe] [PATCH] drm/xe: Prevent null ptr dereference

[Mishra, Pallavi]

> -----Original Message-----
> From: Summers, Stuart <stuart.summers at intel.com>
> Sent: Monday, November 6, 2023 8:31 AM
> To: intel-xe at lists.freedesktop.org; Mishra, Pallavi <pallavi.mishra at intel.com>
> Subject: Re: [Intel-xe] [PATCH] drm/xe: Prevent null ptr dereference
> 
> On Sat, 2023-11-04 at 02:49 +0530, Pallavi Mishra wrote:
> > In scenarios where vm is not initialized, use xe_migrate to get the
> > address.
> >
> > Signed-off-by: Pallavi Mishra <pallavi.mishra at intel.com>
> > ---
> >  drivers/gpu/drm/xe/xe_migrate.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/xe/xe_migrate.c
> > b/drivers/gpu/drm/xe/xe_migrate.c index e6a31f90ebdb..f79ec8e4ae4e
> > 100644
> > --- a/drivers/gpu/drm/xe/xe_migrate.c
> > +++ b/drivers/gpu/drm/xe/xe_migrate.c
> > @@ -1296,7 +1296,10 @@ xe_migrate_update_pgtables(struct xe_migrate
> > *m,
> >
> >                         xe_tile_assert(tile, pt_bo->size == SZ_4K);
> >
> > -                       addr = vm->pt_ops->pte_encode_bo(pt_bo, 0,
> > pat_index, 0);
> > +                       if (vm)
> > +                               addr = vm->pt_ops-
> > >pte_encode_bo(pt_bo, 0, pat_index, 0);
> > +                       else
> > +                               addr = m->q->vm->pt_ops-
> > >pte_encode_bo(pt_bo, 0, pat_index, 0);
> >                         bb->cs[bb->len++] = lower_32_bits(addr);
> >                         bb->cs[bb->len++] = upper_32_bits(addr);
> >                 }
> 
> I also see this in the routine in question:
>         if (first_munmap_rebind) {
>                 err = job_add_deps(job, &vm->resv,
>                                    DMA_RESV_USAGE_BOOKKEEP);
>                 if (err)
>                         goto err_job;
>         }
> 
> so looks like we have a potential for two NPDs here.
> 
> Also in xe_migrate_update_pgtables_cpu:
>         if (wait_vm && !dma_resv_test_signaled(&vm->resv,
> 
> DMA_RESV_USAGE_BOOKKEEP))
>                 return ERR_PTR(-ETIME);

Thanks for reviewing. Let me fix these two as well and resend.
> 
> Thanks,
> Stuart